The present invention relates to a method for decomposing organic compounds containing halogen, i.e. fluorine, chlorine, bromine, and the like such as chlorofluorocarbon group (CFC group, for instance flon), trichloroethylene, methyl bromide, halon, and the like, using a catalyst effectively, and to the catalyst for decomposing organic compounds containing halogen, which maintains its activity for a long time.
Organohalogen compounds such as chlorofluorocarbon, trichloroethylene, methyl bromide, halon, and the like, have been widely used as foaming agents, refrigerants, fire extinguishers, fumigating agents, and others. However, it has been pointed out that the organohalogen compounds cause destruction of the ozone layer of the earth, and give serious influences to the environment such as enhanced generation of carcinogenic substances. Therefore, various methods for decomposing treatment of the organohalogen compounds have been investigated.
As for the decomposing treatment method, combustion technology at an elevated temperature, and plasma technology are main stream. However, these methods have a low energy efficiency because they require a large amount of fuel or electricity and cause a problem of generating damages to the reactor wall by generated corrosive halogen gas. Especially, the plasma method has a large loss of energy when content of the organohalogen compounds in the treated gas is low. On the contrary, a decomposing methods using a catalyst is an effective and superior method, which is capable of treating the gas with low energy if the catalyst has a sufficiently high performance.
As for methods using a catalyst for decomposing organohalogen compounds, the methods using a catalyst containing titania (TiO.sub.2) and tungsten oxide (WO.sub.3) have been disclosed in U.S. Pat. No. 5,292,704 and U.S. Pat. No. 5,176,897. The catalyst disclosed in the above references contains 0.1.about.20% parts by weights WO.sub.3 to 100 parts by weight TiO.sub.2 (the amount of titanium is in a range of 92 mol %.about.99.96 mol %, and tungsten is in a range of 0.04 mol %.about.8 mol % based on Ti and W). The catalyst maintained a decomposition fraction of 99% at 375.degree. C. for 1500 hours in order to treat CCl.sub.4 of ppm order. However, the influence of the organohalogen compounds as catalytic poison is caused by fluorine, rather larger than chlorine. Accordingly, an anti-halogen catalyst, which is scarcely reactive with halogen elements both of chlorine and fluorine, is required.